Ash window cycle ui: don't create mirrored layers for previews until

ash/aura/wm_window_aura.cc

Index: ash/aura/wm_window_aura.cc
diff --git a/ash/aura/wm_window_aura.cc b/ash/aura/wm_window_aura.cc
index 5d925ba952eb1524231b699b5745ecbddde9f7cd..ade4df575c47c6ac9b2af1a214dae310d35992cf 100644
--- a/ash/aura/wm_window_aura.cc
+++ b/ash/aura/wm_window_aura.cc
@@ -690,9 +690,7 @@ void WmWindowAura::SetDescendantsStayInSameRootWindow(bool value) {
 }
 
 std::unique_ptr<views::View> WmWindowAura::CreateViewWithRecreatedLayers() {
-  std::unique_ptr<wm::WindowMirrorView> view(new wm::WindowMirrorView(this));
-  view->Init();
-  return std::move(view);
+  return base::WrapUnique(new wm::WindowMirrorView(this));
 }
 
 void WmWindowAura::AddObserver(WmWindowObserver* observer) {